In the oil and gas industry, a common problem in drilling wells or boreholes in subterranean formations is the loss of circulation materials, such as fluids (for example, drilling fluids or muds), in a well or borehole during the drilling. Such lost fluids typically go into fractures induced by excessive mud pressures, into pre-existing open fractures, and/or into large openings with structural strength in the formation.
A large variety of materials have been used or proposed in attempts to cure lost circulation. Generally, such materials may be divided into five types or categories: fibrous materials, such as shredded automobile tires or sawdust; flaky materials, such as wood chips and mica flakes; granular materials, such as ground nutshells; slurries, whose strength increases with time after placement, such as hydraulic cement; and polymerizable compositions.
Polymerizable compositions comprise one or more monomer, typically, comprising optional components, such as for example fillers, which cure in-situ downhole. Various polymerizable compositions are known and may comprise such polymerizable and/or polymeric materials as an epoxy resin, an organic siloxane, a phthalate resin, a (meth)acrylate resin, an isocyanate-based resin, a polyacrylamide, or the like. For examples see U.S. Pat. Nos. 3,181,611 and 7,696,133; and US Publication No. 2009/0221452 and 2010/0087566; and WO 2010/019535, each of which is incorporated by reference herein in their entirety. More specifically, US Publication No. 2011/0079389A1 discloses the use of a polymerizable composition made of a polymerization initiator and acrylate based monomers polymerizable by frontal polymerization which is activated through an external trigger. Such a process is based on free radical polymerization chemistry.
Although many materials and compositions exist and have been proposed for preventing lost circulation, there continues to be a need for even more versatile and better compositions and methods for preventing loss of circulation.